Tamper indicating security bag

ABSTRACT

A method of manufacturing tamper indicating security bags (e.g for the transportation of cash) from plastic film The method comprises (a) forming an elongate rectangular strip of plastics film material; and (b) folding the opposed long edges of the strip towards the centre to form a pair of flaps with a gap between their inside edges, which leaves the central area of the strip exposed; or the method comprises (a) forming an elongate flattened tube of plastics film material; (b) cutting the tube longitudinally to form a pair of flaps in the overlying material of the flattened tube; and (c) exposing a central area of the underlying material in a gap between the pair of flaps. In either case the method also includes (i) selectively applying layers of adhesive and ink, adapted to form a tamper-evident sealing means, to the central area; (ii) slitting the strip down the middle of the central area to form a pair of elongate folded strips; and (iii) cutting the folded strips transversely at equal intervals, to form individual folded sections of material which can be turned into bags for example by heat sealing the cut edges.

This invention relates to tamper indicating security bags, and particularly to security bags for the transportation of cash or other valuable items. Generally speaking, such bags comprise a body having a closure lip which is adapted to seal the bag in such a way that the contents cannot be accessed, without damaging the seal or the bag in such a way as to render any tampering obvious.

Conventionally, high security bags of this type are constructed with a separate tamper evident tape which is attached to the bag during the manufacturing process, and in a typical example, the tape may be welded to the bag by a heat sealing or sonic welding process, in the case of a thermoplastic bag, or attached by means of an adhesive.

The reason for this method of construction is that it allows the relatively complex layer structure of the tamper evident seal to be pre-formed on a separate tape, rather than on the bag itself.

However, this also has the disadvantage that it creates an inevitable weakness at the junction of the bag and the tape, where the would-be tamperer can potentially disguise the point of entry, by rewelding or regluing after the unauthorised entry. In other words, since there is already a discontinuity in the structure at this point, it will subsequently be difficult to determine whether the discontinuity was part of the original seal, or has been introduced later.

In addition, this construction places a high level of responsibility on the manufacturer, to ensure that the tape is consistently attached to each bag, since again, any variation in manufacturing standards at this point could be difficult to distinguish from an unauthorised attempt at detaching and reattaching the seal.

Similarly, depending on the method of attachment, it may be possible for the tamperer to completely remove the tamper evident tape at its point of attachment and subsequently replace it with tape taken from another similar product. Again, issues of consistency of manufacturing construction will also affect the degree of “tamper evidence” that can be achieved in such circumstances.

Accordingly, the present invention provides a method of forming tamper evident security bags, including a closure with a tamper evident seal comprising a combination of ink and adhesive layers which are formed directly on the material of the bag itself, the method defined in claims 1 and 4 and preferably carried out in order from (a) to (e). It will be appreciated that the layers may be formed on an integral closure lip, or on an area of the body of the bag on which the closure lip is to be sealed, or alternatively, some of the layers may be formed on the closure lip whilst some are formed on the sealing area of the body.

Preferably, in order to ensure that printing ink reliably adheres to a substrate such as polythene, or other similar film material, the surface of the material is treated using known techniques such as corona discharge, gas plasma, or chemicals which effectively etch the surface. In one embodiment of the invention, the surface treatment is made discontinuous, for example by covering the surface with a discontinuous barrier prior to treatment, so as to create predetermined areas of untreated material, and so that a subsequent overall coating of ink or adhesive will not be uniformly attached to the surface, causing a clear pattern to be revealed, in the event that a tamperer tries to reopen the closure.

Alternatively, in another embodiment, the initial surface treatment is applied uniformly, but a discontinuous release layer is formed on top of the surface treatment, so that once again, subsequent layers of ink and/or adhesive will be attached with higher bonding strengths in some areas, and lower bonding strengths in others.

It will be appreciated that the areas of increased release effect may, for example, be in the form of a message or symbol so as to render the evidence of tampering much more obvious.

The seal may also incorporate one way temperature reactive inks, such as thermo-chromic ink, which also enables the bag to show evidence of tampering if it is subjected to heat, cold, or the like, as well as mechanical manipulation or chemical attack. Preferably, the arrangement of the tamper evident ink layers is such that they are enclosed on both sides, that is to say, by the film substrate on one side, and by a layer of adhesive on the other side, so that it is also possible to reduce the risk of pre-tampering. This refers to a scenario in which the would-be tamperer pre-treats the closure device by interfering with the tamper-evident layers before the bag is closed, so that it can be subsequently opened without tamper evidence.

According to a further preferred feature of the present invention, the bag is formed from a strip of material which is folded over, to form a bag having a front and a rear wall of material connected by a fold forming the inner end, whilst one of the wall sections is left longer than the other, so as to form a closure lip. The side edges of the bag may be heat sealed or otherwise welded together, with the heat seals incorporating so-called “security printing”. Similarly, by starting with an elongate strip whose width is at least four times the intended bag length, it is possible to produce bags in “two-up” formations by folding both free edges of the strip inwards towards the middle. In this way, a continuous fold is formed along each of the opposite edges, providing respective overlap portions. This enables a series of pairs of bags to be formed, which are then separated by slitting the assembly lengthwise down the middle. Preferably, in either case, before the folded portions forming the individual bags are finally cut from the entire length, any required printing of adhesive, or ink, or other pre-treatment of the surface, can be carried out in a continuous fashion, on the central area in the region of the folded over edges.

Alternatively such pairs of bags can also be produced starting with a continuously extruded tube of film which is flattened and then slit longitudinally, so as to form a pair of facing overlap portions.

Some embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic perspective view illustrating a first known process for making tamper evident security bags;

FIG. 2 is a diagrammatic perspective view of a known arrangement for making security bags;

FIG. 3 is a diagrammatic perspective view of a preferred method for making bags according to the present invention together with bags so made;

FIG. 4 is another perspective view of the method according to the present invention;

FIG. 4 a is a detailed expanded view of part of the drawing of FIG. 4 a showing a stage in the printing process;

FIGS. 5 a to 5 h show a plan view of the tamper evident region of the bag as layers of tamper evident features are added;

FIGS. 6 a to 6 h show schematically the shown in plan in FIG. 5 a-5 h.

FIG. 7 shows a cross sectional view of the partially formed bags shown in FIGS. 5 h and 6 h and FIG. 7 a shows an enlarged portion of a part of FIG. 7;

Referring to the drawings, FIG. 1 shows a basic method for making security bags from a roll of thermoplastic film 2, in which the web of material is folded in half to form a bag 1 (once the sides are sealed) and has a security tape 3 attached to the mouth to form a tamper evident seal. The tape itself can be made from a similar single wound sheet which is then slit into multiple “lanes” for example ten across. Security printing in suitable patterns will generally be applied to the web, before it is split into the individual tape sections.

In order to produce bags with an integral security feature, on the other hand, as shown in FIG. 2, a roll 4 of a web which has already been folded in half, as indicated by overlapping sections 6 and 8, can be printed down one edge 10 with security printing, before individual bags 12 are cut from the strip. As illustrated, the underlying folded part of the web 8 is made longer than the overlying part 6, so that the edge 10 extends far enough to form a closure lip for the mouth 14 of the bag, once the side edges 16 and 18 have been heat sealed.

It will be clear, however, from the illustration on FIG. 2, that this method only allows one bag to be made at a time on the roll, and in view of the fact that attaching a separate tape allows so many more tamper evident portions to be made for a given width of single wound sheet, the method described with respect to FIG. 2 has only been used to prepare very basic tamper evident security bags with very few tamper evident features, for example, a single layer of solvent detecting ink coated with adhesive.

FIGS. 3 and 4 illustrate an improvement on this process, in which the roll 20 of plastics material consists of a much wider continuous strip which has been folded inwards from both long edges 22, 24, so as to form a “C” shape leaving an exposed open region in the central area of the lower web 26, between the edges 22 and 24 of the flaps formed by the folding. security printing and (for example) receipt areas can then be printed in the exposed region in the central area, thus preforming a series of facing pairs of bags joined by their closure lip portions in the region 26, before separating them by slitting down the central line 28.

A similar result of C-shaped film with a central gap between two flaps can be achieved from an extruded “tube” of film, by cutting it longitudinally down one side. There are two methods starting with at tube, in both cases, the tube is flattened and stored on a roll. Then, either a longitudinal strip is cut from the centre of the overlying material to expose the central area of the underlying material, or a longitudinal slit could be cut down the length of overlying material of the tube and the inside edges of the material along the slit could be urged apart, for example by “ploughing”.

In order to make the bag according to the invention, having formed the C-shaped web shown in FIGS. 3 and 4 by one of the abovementioned methods tamper evident features are applied to the lower web in the central area 26 between the inward edges 22, 24 of the flaps as follows with reference to FIGS. 5 a-h and 6 a-h. It will be seen that the same features are applied in two lanes which can be mirror images about the central dividing line 28:

A first layer of ink 51 is applied in a pattern (in this case in the form of a pair of lines spelling void) directly onto the (preferably transparent/translucent) central area of the lower web (see FIGS. 5 a and 6 a).

Next the central area 26 is treated to improve the adhesion of ink, for example by corona treatment 52 (see FIGS. 5 b and 6 b). These two steps form a release layer because the ink printed before corona treatment will not adhere to the surface on which it is printed. An alternative would be to first treat the whole area then apply a release layer such as silicone.

Third, as shown in FIGS. 5 c and 6 c a preferred step is carried out whereby a mask of text 53 is applied to the region of the release layer to mask the shadow of the release pattern.

Fourth an ink 54 is applied over the release layer as shown in FIGS. 5 d and 6 d. This may be followed by a second layer of ink 55 (shown in FIGS. 5 e and 6 e) if necessary, to improve the opacity of the ink covering the release pattern 51 and thicken the ink layer, so that a more significant air gap is produced when tampering occurs which leaves some ink attached to the closure lip and the part coating the release pattern adhered to the opposing surface of the closure.

In a sixth step (shown in FIGS. 5 f and 6 f) a thermochromic ink 56 is applied to the (preferably transparent/translucent) central area of the web 26 in a region away from the release layer and coating ink layers, such that tampering by heating/cooling the closure is revealed.

The seventh step is shown in FIGS. 5 g and 6 g—in this step an adhesive 57, e.g. hot-melt adhesive is applied to the central portion covering all the tamper evident features referred to above. In order to provide a double-seal, prior to applying the adhesive the inside edges 22, 24 of the flaps are urged away from one another to expose a greater area of the central region of the web 26 such that the adhesive can be applied to the region which will form the closure lip and in a region under the mouth of the bag which will face the opposite side of the bag. Line 60 in FIG. 5 g represents the position where the flaps will return to when they form the mouth of the bag and it can be seen that the adhesive extends further inwards (2 mm inside the mouth of the bag would be enough, but greater than 1 mm could be acceptable and much wider, e.g. 10 mm would be effective if somewhat unnecessary).

In the eighth step shown in FIGS. 5 h and 6 h a release liner 58, e.g. foil is applied over the adhesive.

FIG. 7 shows a cross sectional schematic view through the web after the eight steps referred to above have taken place and following the eighth step the inside edges 22, 24 of the flaps have been returned to the position they will take up when the web is cut and sealed to form bags. The tamper evident features 51-56 appear on a part of the closure lip which will be folded over in use to seal the mouth, but the adhesive 57 extends 2 mm below the mouth of the bag and the release liner 58 extends an additional 2 mm into the bag beyond the adhesive and a further amount, e.g. 1 mm over each side of the adhesive to avoid accidental attachment. At some stage it is preferred to form a receipt portion 59 by printing on the central area 26 and forming perforations between the receipt portion 59 and the tamper evident portion.

Once the security features have been applied, the web is cut and sealed laterally to attach the flaps to the web underneath, such that the web forms a rear wall and the flaps become the front walls of the bags. The lateral cutting and sealing (e.g. heat welding) would normally take place at equal intervals to form bags of equal width.

FIG. 8 illustrates a finished bag made by a process such as that of FIGS. 3 to 7( with the release liner removed), in which a “rear wall” 30 (i.e. the underside as shown in the drawing) is made longer than the “front wall” 32 (the top surface as seen in the drawings) so as to provide an outwardly extending closure lip 34, the “closed end” 36 of the bag being formed by the fold joining the front and rear walls. In the example shown, a “fugitive ink” 38 that is to say one which is soluble in water or spittle, is printed in a suitable pattern, on the outside area of the front wall which is to be overlapped by the closure lip in use, whilst the closure lip itself includes the tamper evident features 51-55 in parallel strips separated by the strip of thermochromic ink 56.

Of course, as mentioned above a layer of hot melt adhesive 57 has been applied over the whole area of the closure lip, and also extends into the opening of the bag, but the adhesive is clear and cannot be seen in FIG. 8. When the liner is removed, the rear surface of the edge 22, 24 of the front wall can be sealed down, before the closure lip 34 is folded over, and sealed on to the front surface 32.

In this way, a “double seal” is formed at the mouth of the bag, which greatly improves the “tamper evident” capability of the assembly.

It will be noted that FIG. 8 included a receipt portion 59 at the top of the bag, however, the receipt portion need not necessarily be at the top of the bag and without the receipt portion at the top, the tamper evident portions of the two simultaneously manufactured bags could be printed closer to each other and the central line 28. in this case, a receipt portion could be manufactured at the closed end 36 of the bag, provided a seal was made further up the bag. Such an embodiment is shown in FIG. 9 in which like reference numerals refer to like parts, and a seal at the bottom of the bag is represented by numeral 61 with perforations 60 shown beneath the seal to allow the receipt to be detached. 

1. A method of forming tamper-evident security bags from plastics film material, the method comprising: (a) forming an elongate rectangular strip of plastics film material, the formed strip having opposed long edges, a center, and a central area having a middle; (b) folding the opposed long edges of the strip towards the center to form a pair of flaps with a gap between the opposed long edges, which leaves the central area of the strip exposed; (c) selectively applying layers of adhesive and ink, adapted to form a tamper-evident sealing means, to the central area; (d) slitting the strip down the middle of the central area to form a pair of elongate folded strips; and (e) cutting the elongate folded strips transversely at equal intervals, to form individual folded sections of material.
 2. A method according to claim 1, wherein cutting the elongate folded strips transversely further includes heat-sealing edges created by the cutting, so that the individual folded sections are formed into individual open-ended bags.
 3. A method according to claim 1, wherein layers of adhesive or ink are also applied to the opposed long edges of the strip in a region adjacent to the central area of the strip.
 4. A method of forming tamper-evident security bags from plastics film material, the method comprising: (a) forming an elongate flattened tube of plastics film material, the flattened tube comprising an overlying material and an underlying material; (b) cutting the tube longitudinally to form a pair of flaps in the overlying material of the flattened tube; (c) exposing a central area of the underlying material in a gap between the pair of flaps; (d) selectively applying layers of adhesive and ink, adapted to form a tamper-evident sealing means, to the central area; (e) slitting the central area to form a pair of elongate folded strips; and (f) cutting the folded strips transversely at equal intervals, to form individual folded sections of material.
 5. A method according to claim 4, wherein (b) cutting the tube and (c) exposing the central area of the underlying material are completed by cutting a strip of material out of the central area of the overlying material.
 6. A method according to claim 4, wherein (b) cutting the tube further comprises cutting a slit along the center of the overlying material of the tube and wherein (c) exposing the central area further comprises urging the edges of the pair of flaps apart.
 7. A method according to claim 4, wherein cutting the folded strips transversely further includes heat-sealing edges formed by cutting, so that the folded sections are formed into individual open-ended bags.
 8. A method according to claim 4, wherein layers of adhesive or ink are also applied to the central area of the underlying material underneath an edge of the overlying material adjacent to an opening of the bags.
 9. (canceled)
 10. A tamper evident security bag comprising: a mouth; an integral closure lip; and a tamper evident feature on the closure lip, the tamper evident feature comprising: a patterned release layer, a coating ink layer applied over the release layer, a thermochromic ink applied in a region away from the release layer and the coating ink layer, and an adhesive, wherein the adhesive is applied to the closure lip covering the tamper evident feature and in a region under the mouth of the bag which faces a side of the bag opposite the closure lip.
 11. A tamper evident bag according to claim 10, wherein the patterned release layer is formed by a first layer of ink applied in a pattern directly onto the closure lip prior to corona treatment.
 12. A tamper evident bag according to claim 10, further comprising a mask of text applied to a region of the release layer to mask any shadow of a release pattern formed by the patterned release layer.
 13. A tamper evident security bag according to claim 10, further comprising a second layer of coating ink to improve opacity of the coating ink covering the patterned release layer and to thicken the coating ink layer, so that a more significant air gap is produced when tampering occurs which leaves some ink attached to the closure lip and some of the ink coating the patterned release layer adhered to an opposing surface of the closure lip.
 14. A tamper evident security bag according to claim 10, further comprising a release liner, applied over the adhesive.
 15. (canceled)
 16. (canceled)
 17. (canceled) 